The Third Generation Partnership Program (“3GPP”), Release (“Rel”)-13 (which is incorporated herein by reference along with all other Releases set forth herein) includes features to suspend and resume radio resource control (“RRC”) context. The general idea is that when a user equipment (“UE”) session ends and the UE goes to an RRC idle state, both the UE and the radio access network (“RAN”) keep a passive UE context. This passive UE context can be re-activated with a slim resume procedure. The use of the resume procedure leads to a fast setup of radio communication resources, which means low latency for the communication system including the UE, and efficient execution of the procedure therein.
When the UE requests re-activation (resume) of a passive UE context, the UE signals an identifier to the RAN so that RAN can find the passive UE context to re-use and re-activate this context. Since the new access can be done in another communication node (e.g., another base station) of the RAN than where the passive UE context is stored (i.e., an initial communication node or initial base station), the identifier should include an identity of the initial communication node. Consequently, the another communication node can locate the initial communication node that holds the passive UE context.
In a 3GPP Long Term Evolution (“LTE”) communication system, the mechanism for establishing or re-activating a connection may be sent on a common control channel (“CCCH”). The CCCH is associated with logical channel identifier (“LCID”) 0 in the media access control (“MAC”) layer. In the 3GPP LTE communication system, a unique base station identifier (or in short “eNBId”) within a public land mobile network (“PLMN”) is built up from 20 bits.
As mentioned above, the request from the UE to re-activate the passive UE context should include a unique identifier for the initial communication node holding the passive UE context. Typically in the 3GPP LTE communication system, a UE is identified with a system architecture evolution (“SAE”) temporary mobile subscriber identity (“TMSI”) including 40 bits, but this does not fit the “message 3” together with the unique base station identifier (eNBId). Thus, the length of the identifier may exceed the frame size for the messaging within some communication systems.
The identifier should be large enough to cover the expected large number of passive UE contexts for a base station where the 3GPP LTE communication system is operating with the suspend and resume functionality. Therefore, support for a larger identifier would be beneficial, but still keeping in mind flexibility to enhance (or optimize) latency and performance in normal cases.
The RRC message in the 3GPP LTE communication system that may carry this information (resume id among other things) is an RRC message in the resume procedure (typically called a “message 3”). In legacy procedures, this is called an RRC connection request. The “message 3” refers to a signal in an LTE random access procedure and may contain more than just the RRC connection/connection resume request, e.g., MAC control element(s) or service data units (“SDUs”) from other logical channels depending on the use case. An RRC connection request is an RRC message sent in the message 3 in the legacy LTE during attempts to establish an RRC connection. In other situations, the message 3 may include other information. The message 3 in the LTE may include 56 bits. The radio access node can choose to provide resources for a larger message 3, albeit at the expense of coverage and/or expanded delay. The message 3 can carry 72 bits in existing technologies and there are reasons to maintain the message size to allow the resume procedure to work with legacy procedures and performance. While the 72 bits can accommodate the 40 bits for the S-TMSI of the UE, it cannot incorporate the unique base station identifier, which may be on the order of 20 bits. It would be beneficial, therefore, to incorporate a flexible UE identification that, for instance, can accommodate a unique base station identifier for the resume procedure.